Turbine blade shroud fastening apparatus



April 6, 1943. J. F. CHALUPA ET AL 2,315,594

' TURBINE BLADE SHROUD FASTENINQ APEfARATUS Filed Jan; 16, 1942 l :6 I7 I l lluh i l l ll W n.

WITNESSES:

INVENTORS Joss u F. CHnwPn In:

WgunM H-LLOYD.

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ATTORNEY Patented Apr. 6, 1943 TURBINE BLADE SHROUD FASTENING APPARATUS Application January 16, 1942, Serial No. 426,966

UNITED STATES PATENT OFFICE 2 Claims.

The invention relates to elastic fluid turbines, more particularly to blading thereof, and it has for an object to provide a row of blades having individual integral shroud elements arranged circumferentially in end-to-end relation with improved means for tying the blades together in groups such that manufacture may be facilitated and adequate strength preserved without concentration of stresses in the structure serving this purpose.

Turbine blades having contiguous shroud elements provided with outer tenons connected by arcuate shroud or tie bands are old; however, due to centrifugal and vibratory effects of the blades, the band may be subjected to concentrated stresses at regions thereof immediately over the contiguous edges of the shroud elements. tendency of these edges to offset radially due to said effects is resisted by the tie band and this action may result in severe stresses in a section of the band immediately over the edges. thermore, due to inevitable small variations in manufacture, true alignment of the shroud elements may not occur with the result that adjacent outer corners may be offset, and such offset corners of greater radius may cause an initial concentrated stress condition incident to fastening a band to the blades of a group. Therefore, a further object of the invention is to avoid this concentrated stress condition by relieving the shroud elements adjacent to the contiguous edges.

A further object of the invention is to provide blades having contiguous shroud elements provided with tenons connected by arcuate shroud bands wherein the shroud elements are so formed that the middle portions of their outer surfaces fit against the inner surfaces of the shroud bands and wherein the marginal portions of such surfaces adjacent to the contiguous edges are rounded so as to form cusp-like spaces with respect to the inner surfaces of the bands, whereby concentrated stresses at a section or localized zone of the band due to corner action of shroud elements is avoided.

These and other objects are effected by the invention as will be apparent from the following description and claims taken in accordance with the accompanying drawing, forming a part of this application, in which:

Fig. 1 is a fragmentary View of a row of blades having the improved shroud arrangement applied thereto;

Fig. 2 is a sectional view taken along the line IIII of Fig. 1;

Fig. 3 is a fragmentary sectional view of outer portions of adjacent blades and connecting tie bands; and,

Fig. 4c is a fragmentary isometric view of the Referring to the drawing, the blades I are arranged in a row, at l I, carried by the rotor or Each blade comprises a root element [3 for attaching the blade to the rotor, a blade element It, a shroud element l5, and a tenon l6 extending outwardly from the shroud element. When assembled in the row, the contiguous shroud and root elements define outer and inner boundaries The blades are connected in arcuate groups by means of the tie bands H, the bands having openings through which the tenons extend and being held in place by headed or riveted portions (8 of the tenons which overlap the bands around The shroud elements l are relieved adjacent to the contiguous edges thereof so as to avoid the possibility of the corners acting on the bands to set up sections or localized zones of concentrated This result is preferably accompanied by forming each shroud element so that the middle portion [9 of its outer surface extending widthwise of the blade row engages the inner surface of the band and the adjacent marginal portions 20 are rounded so as to define cusp-like clearance spaces 2| with respect to the inner surfaces As the junctions of the surface portions l9 and 20 are substantially a tangent relation, there is no corner provided thereby, with the result that, in the event of blade deflection, instead of the opposing effect of the band being manifested by a condition of concentrated stress over a cor ner, the band stresses are distributed over a greater circumferential length, and the structure, on that account, has greater mechanical Furthermore, due to inevitable small variations in manufacture, it is practically impossible to secure true alignment of. the shroud elements; and, for this reason, if the marginal portions were not rounded, there would be offset outer The corners of greater radius would not only interfere with proper fitting of the bands but the localized deformation thereof incident to fastening would result in an initial While the invention has been shown in but one form, it will be obvious to those skilled in 5 shroud end portion of a blade.

disk [2.

for the blade passages.

Any

Furthe openings.

stress.

of the bands.

strength.

corners.

state of stress concentration.

the art that it is not so limited, but is susceptible of various changes and modifications without departing from the spirit thereof, and it is desired, therefore, that only such limitations shall be placed thereupon as are specifically set forth in the appended claims.

What is claimed is:

1. In an elastic fluid turbine, a row of moving blades providing blade passages; shroud elements integral with the respective blades and. arranged circumferentially in end-to-end relation to form a shroud construction covering the blade passages; and means for connecting the blades in groups comprising tenons which are integral with the respective shroud elements and which spring from and extend outwardly from the outer surfaces of the latter, segmental tie bands having openings through which the tenons extend, and headed or riveted portions provided by the tenons in overlapping engagement with respect to the tie bands to hold the latter in place with respect to the shroud elements; the shroud elements being so formed that middle portions of the outer surfaces thereof and extending width- Wise of the blade row engage the inner surfaces of the tie bands and the adjoining outer portions of the outer surfaces are in tangent relation with respect to the middle portions of such surfaces and diverge from the inner surfaces of the tie bands.

2. In an elastic fluid turbine, a row of moving blades providing blade passages; shroud elements integral with the respective blades and arranged circumferentially in end-to-end relation to form a shroud construction covering the blade passages; and means for connecting the blades in groups comprising tenons which are integral 7 With the respective shroud elements and which spring from and extend outwardly from the outer surfaces of the latter, segmental tie bands having openings through which the tenons extend, and headed or riveted portions provided by the tenons in overlapping engagement with respect to the tie bands to hold the latter in place with respect to the shroud elements; the shroud elements being so formed that middle portions of the outer surfaces thereof fall substantially within a cylindrical surface whose axis is the turbine axis so as to contact with inner surfaces of the tie bands and merge into marginal surface portions which are curved so as to diverge from the inner surfaces of vthe tie bands.

JOSEPH F. CHALUPA.

WILLIAM H. LLOYD. 

